Leonids november 16/17: results from Marco Langbroek and Robert Haas, Meppen, Germany

Dear Everybody,

We have tried a campaign on the night of 16/17, both visual and
multistation photographic, in the Dutch/German border area. Though not the
entire night, we have been able to observe. Below our impressions.

Team 1 (Koen Miskotte, Carl Johannink and Jos Nijland) was at Lattrop
public observatory in the easternmost part of the Netherlands and could
observe for two hours from about 0:15 to 2:30 UT

Team 2 (Robert Haas and me (=Marco Langbroek)) made a 'grand tour' through
norteast Netherlands and parts of Germany, tried to find a location without
haze and stratus. We found it near Meppen, only just over the Dutch/German
border (but it later turned out that it had been better if we had gone some
30-50 km more to the east). We observed from 1:45 to 2:45 UT. Then, a
cirrus front coming from the west that also hit Lattrop culled us off.

Both stations had Lm near ~ 5.4-5.7. Rates were clearly enhanced, but not
as much as we had hoped for. We don't have our data available yet, but our
impression is, trying to account a little bit for the moonlight, that rates
were similar to the 1995 return, i.e. ZHR around 30-40 or so. What struck
us was that in comparison with both 1995 and 1996 there weren't that much
real bright meteors. The Lattrop team however has seen one -6, with 3
minutes persisting train. I saw a -2 as my brightest during my session, and
a -4 tru cirrus in twilight when back at Lattrop. To be clear: the meteors
were certainly brighter than the normal annual display, but not to the
extend as in 1995 and 1996.

So, a little bit ambiguous. We are glad to have been able to do some
observing, especially given that last days in the forecast it didn't look
like we would be able to do so. And yes, there was a fine enhancement. But
from the perspective of rates and brightness, it could have been better.

That's it for the moment. We are now back again at Casper's place to look
at the forecasts for coming night and the last satellite pictures.
Probably, we will be active from the eastern part of our country again,
which when we left had good clear skies (the cirrus had dissolved). Problem
is that the electricity generator of team 1 has broke down, so we have to
position them somewhere where they have an electric socket available (such
as at a public observatory).

-Marco Langbroek
Dutch Meteor Society, the Netherlands

Also on behalf of:
Koen Miskotte
Jos Nijland
Robert Haas

Leonids november 17/18: results from Marco Langbroek and Robert Haas, Biddinghuizen

Hello everybody,

This is a weird campaign. Last night (early in the evening) it looked like
we would have to go to the east of our country again. We had already left,
when we received word that there could possibly be cloud interference coming
from |Germany in the east later that night, but.....that the center of our
country was clearing! One of our 2 teams already had reached the publ;ic
observotory at Lattrop in the east of the Netherlands, but Robert and I were
just 30 km east of our regular location Biddinghuizen and decided to turn
and go to that location.

When we arrived, the sky was as clear as crystal. Much to my amazement, I
counted an Lm of 6.0, which is perhaps the best I have ever experienced for
moonlight conditions! We could even see some marginal milky way from
Cassiopeia to Cygnus! So we decided to stay and setup. After setting up our
photographic equipment, we took a short sleep, and started observations
fresh (...) at around 0:45 local time (23:45 UT).

In the early part of observations, the Leonids were showing a clear
activity, though evidently less than the previous night. Several attractive
bright meteors up to -3 appeared. But later that night, rates were
evidently and seriously in decline: we really experienced (so to speak) that
they did fall off markedly, the stream just petterred out so to speak. It
was brilliantly clear, but also frosty (temperatures slightly below
freezing) and the eastern wind was strong and very cold. The last hours were
really unpleasant because of the cold wind and the actually quite unaspiring
activity around that time.... Meteors now seemed less bright too.... But our
perseverance was rewarded with a beautifull brilliant blue -6 Leonid at
5:12:16 UT that had 2 minutes of persisting train, drifting gently away....

This night, we also saw some nice Taurids including a loooooooooong -2.

Tomorrow or the day after, I will mail my data of last two nights. Like I
wrote before, definitely enhanced activity, a nice show (particularly 16/17
and early in the night 17/18, but less than we had hoped for and in that
aspect slightly disappointing. But it was a good campaign.

Last night we certainly obtained some multistation photographic orbits of Leonids.

-Marco Langbroek
Dutch Meteor Society, the Netherlands

Leonids 1997: results from Koen Miskotte and Marco Langbroek of 16/17 and 17/18 november

Hello,

Below the data of Koen Miskotte and me (=Marco Langbroek) of 16/17 and 17/18 november.

(Rainer: I will not send this set tru postal mail, so this is my only submission -ML)

Moonlight, but extremely clear. Even part milky way marginally visible!

Note: Both Koen and I suggest to be somewhat cautious in regard to the
meteor magnitude estimates. Perhaps, we slightly estimated to faint
because of the moonlight.

-Marco Langbroek

Leonids 1997: More preliminary ZHR results (Europe too)

Hello again,

Below some VERY preliminary ZHR-results from our Dutch observations, to
add to the preliminary ZHR for california I communicated earlier. Again:
please regard this as an indication of rate level only. It is based on
data from 3 observers: Carl Johannink, Koen Miskotte and me (=Marco
Langbroek).

In general, ZHR's were around ~50 for early november 17 as observed from
Northwest Europe. Unfortunately, our observing interval was short due to
clouds. The next night, 17/18, saw a ZHR that decreased clearly over the
night, from about ~40 to ~30. Coupled to the ZHR ~115 seen from
California (note: based on Bob's data only, so be carefull!), this agrees
excellently with a B~1 component peaking at around ZHR ~115 (annual +
outburst combined: outburst only ~100) above the western USA, with B
describing rate behaviour as in the next equation:

ZHR = ZHR_max * 10^-B|l-l_max| (See Astron. Astroph. 295 (1995), 206)

...with l= solar longitude

This means that a similar broad B ~1 (and bright) component as in
1994-1995-1996 has been present, this time with a peak ZHR near 100.

It is not clear whether a narrow peak was also present, as in 1996.
Perhaps Bob and some others saw the onset after 13:00 and the narrow peak
then might have peaked just after the end of the Californian time window,
over the western Pacific perhaps. But as George noted, 'storm'-rates have
not been seen by Californians themselves, judging from the reports and
Bob's data.

Below some ZHR's for the European intervals, as described above,
calculated for r=2.0 with gamma=1.4 and perception taken into account
(Carl: 1.0: Koen: 1.2; Marco: 1.4).

Nov 17
UT ZHR +-
1:30 50 8
Nov 18
UT ZHR +-
1:45 42 5
3:42 28 4

Add these to the values from Bob's observations from west USA send
earlier (ZHR's around 115, except for last hour which might have been
higher). The outburst was present for about one day, with Europe seeing
rates going up the one night and down the other, and the USA having the
privilege of the peak.

Results of 1997 November 17
My Radio-observations of the Leonids started in 1993. Since the new season
of the Leonids started in 1994 this is the most active one that I have observed
by forward-scattering of VHF radio waves.
Forward-scatter observations of long-duration reflections > 7 seconds
(oncorrected counts) starting at UT:
5h 6h 7h 8h 9h 10h 11h 12h 13h
21 19 22 22 13 20 16 4 4
(14) (12) (10) (18) (5) (8) (6) (1) (1)
Between brackets the number of long-duration reflections > 20 seconds.
Between about 8 and 9h UT many long-duration reflection > 100 seconds.
Possible first maximum between 10h and 11h30m UT (Solar Longitude: 235.17)
Because Radiant below horizon no data around nodal passage.
In 1996 a Radiomaximum is observed at Solar Longitude 235.16 and 235.27)
Notes: For the mid-point of the transmitter-receiver path:
Radiant rising on November 16 at about 21h30m UT.
Radiant setting on November 17 at about 13h40m UT.
Most favourable antenna-geometry for detecting Leonids:
between 5h45m and 7h30m UT.
Unfavourable antenne-geometry after 10h UT.
Very unfavourable antenne-geometry after 12h UT.
Radio Hour Rates of the Leonids of 1997 November 17
Very preliminary results!
After correction of 'dead-time", "sporadics" and Observability Function after
Hines, the very preliminary results of my radio-observations are given.
| For this period the results are NOT reliable
| because the very unfavourable antenna-geometrie
___________________________________________________________________________________
|
5-6 6-7 7-8 8-9 9-10 10-11 | 11-12 12-13 13-14 (Time in UT)
29 22 26 29 20 64 | 43 30 30 (Hour rates)
(6) (5) (5) (6) (6) (14) | (13) (20) (20) (one-sigma errors)
Probably a first maximum is observed between 10h and 11h30m UT,
nearby Solar Longitude 235.17 degrees (Equinox 2000.0). Almost on the same position
as observed in 1996. A "nodal" peak is not monitored because for the mid-point of
the transmitter-receiver path the radiant was on that time below the horizon.

Preliminary Results of Radio Meteor Scatter observations of the Leonids 1997

Since my radio observations of the Leonids started in 1993, and the
observations show evidently that the new season of the Leonids started in 1994,
the Leonids of 1997 were the finest of all because the very long period of high
activity on November 17 with many long-duration reflections often over more than
>100 seconds.

The first clear Leonid is observed on November 15. However, the total
activity on this day was very low.

Radio Hour Rates (RHR) of about <2.

On November 16 the activity of the Leonids was slightly increased and
a mean RHR of about 6 is found between 6h and 11h UT. On November 17, the higher
activity started probably after 0h UT, because until this time no unusual activity is
monitored above the "sporadic" activity. When I started my observations again at
4h50m UT the Leonids were already very active. Until 12h UT, high rates are monitored.
The mean RHR in this whole period is about 40. After 12h UT the antenna-geometry was
very unfavourable and therefore the Radio Hour Rates are unreliable. Probably a peak
is observed around 11h UT at Solar Longitude 235.17 degrees (Equinox 2000.0). Almost
on the same place as observed in 1996 at 235.16 degrees. At the moment the Earth passes
through the orbit plane of comet 55P/Tempel-Tuttle the radiant of the Leonids was just
below the horizon. Therefore a peak is not monitored as observed in 1996 around Solar
Longitude 235.27 degrees. Because activity was still monitored after 12h UT, perhaps
rates were higher in the last hour. On November 18 the activity was still high with a
very constant RHR of about 10.

Below all the Radio Hour Rates are given. All are corrected for dead-time (*),
sporadics and observability function after Hines[1].

Between brackets one-sigma errors with the errors of sporadic activity taken into
account.

Please note on 72 MHz, I can only receive Leonids of about visual magnitude +2 or
brighter!

(*) Dead-time marks the period in which a certain signal of amplitude may mask other signals of lesser amplitude.

The dead-time were applied according to the "Geiger-counter method".

[1] Hines, C.O., Can. Journ. Phys. 22, pp. 493-503, 1955

Leonids 1997: results from Carl Johannink and team at VST-Lattrop

VISUAL RESULTS LEONIDS 1997

Clear skies in november are very rare in the Netherlands, especially during the Leonids.
But 1997 is an exeption! The night 16/17 was partly clear and 17/18 completely.
Unfortunately I had to go to work both days. Beiing a teacher isn't always the ideal job...
So I observed these nights only for some hours.
Below are the results.
Observing with Rita Verhoef, Arnold Tukkers, Ralf Mulder,
Patrick Schiphorst from our Observatory, and Koen Miskotte and
Jos Nijland from 'Biddinghuizen' was very pleasent.

The 1997 Leonids showed a major event over the western part of the USA.
Between 4:00 and 4:30 local time (12.00 - 12.30 UT), tens of fireballs
were seen by observers in Southern California. There was a period in
which about one fireball of -4 or better was seen every minute.
Several of them -10 or so. Many long enduring persistant trains
were reported. Due to the bright moonlight, no faint meteors were seen.

A three station photographic network was set up by the members of the
Californian Bay Meteor Society in cooperation with the Dutch Meteor
Society which set up the third station at Edwards Air Force Base.
Despite the bright moonlight and the moon nearly in its zenith, it was
possible to make good photographs because of the very transparent sky
we had at maximum night and the night before. We expect at least
40-50 bright Leonids and fireballs to have been photographed, many of
them multi-station photographs. The California stations were set up at
Walker Pass (where a small earthquake was also felt!) and at Goldstone
test site.

The Dutch station at Edwards Air Force Base was set up in close
cooperation with a Canadian radar and video project set up by the
NRC (Peter Brown).

-10m Leonid fireball. November 17, 1997 12h11m55s UT. Appeared less than 20 degrees from the moon
and nevertheless produces a bright flash and shadows. A long enduring tran was seen during ten minutes
in broad moonlight.
Edwards AFB. Camera : Canon FD f/1.8-50 mm. Rotating shutter at 50 breaks/second.

Please note: you will need a MJPEG-AVI driver to play these movie-files on your
computer! Your computer will probably not have such a driver installed, as it is not
part of the Windows'95 installation. A good driver is the one form
PARADIGM.
Download will start immediately when you click on the link. Installation instructions
are on the PARADIGM-website.

While no one reported seeing anything close to the historically known
"meteor storms" from Last Monday night's Leonid meteor shower, many
observers were nevertheless impressed by many bright fireballs. According
to S&T contributor Stephen O'Meara, who was observing from the slope of
Hawaii's Mauna Loa, there were several instances when the fireballs came in
clusters of four or five. The brightest meteor, he reports, was magnitude -4
(as bright as Venus), and exploded with a brilliant white flash and left
a train that lasted more than 5 minutes despite the moonlight. His maximum
rate was between 13 and 14 hours Universal Time when he observed 41
meteors. The meteor trains varied in color from orange to green. Because
the Leonid shower's parent comet 55P/Tempel-Tuttle is due to reach
perihelion in February, meteor observers were hopeful that the display
would be extra intense. However, it is more likely that the "storm" may
come in 1998 and/or 1999.

I have done some very (VERY) preliminary calculations, using Bob
Lunsfords data, to get some insight into the Zenit Hourly Rates (ZHR)
experienced for the maximum period, which California presumably
experienced or was very close at. You find them below.

Please note that this is very preliminary, and based on one observer
only. So, it is only an indication (emphasis) of the ZHR levels. I choose
Bob's data for several reasons: he reports a good Lm, made a good set of
data available, and from earlier work with his data I now he has a
perception which is quite the 'average' or 'standard'
perception (i.e. Cp ~1.0). His sporadic rates combined with reported Lm's
hint that his perception did not seriously alter due to the moonlight
conditions. So for an indication, I think his data will suffice.

I calculated ZHR's in ~1 hour intervals, with gamma 1.4 in radiant
altitude dilution (gamma 1.0 would result in only slightly lower rates).
I give two ZHR's: one under the assumption of a population index r=2.0,
and one for r=2.5. The first assumes emphasis on bright meteors, the
second assumes a faint component similar as what we saw in 1996 (but
almost unnoticable due to the moonlight). For the moment, I think the
r=2.0 column is most appropriate. In the last column, I give Bob's
limiting magnitudes for reverence, because variations in Lm of course
might influence rates slightly.

Please note the moonlight circumstances, so take it as an indication only.

Activity seems rather constant at just above ZHR 100. Perhaps, rates
where higher in the last hour, but this is sensitive to the Lm estimate
(the effect disappears largely if the true Lm was higher). But the report
of increased fireball occurence during this last hour suggest that rates
might really have been higher (perhaps peaking after twilight set in?).
During our 1996 European narrow peak we also experienced a fireball
flurry besides the faint meteors (both Koen and me personally saw at leat
12 Leonids of -3 and brighter in one hour).

I did not look at our Dutch results yet (still have to listen to my
tapes: due to some personal circumstances that was not possible untill
now. Koen will report his data within 1-2 hours from now to me), but if
our estimate of ZHR 30-40 during our European Nov 17 night interval is
correct, this would pretty well line up with the rates at about 100 or
slightly higer for California. It suggest a B~1 structure, like
1994-1996, peaking over west USA/east Pacific.

The 1997 Leonid peak was expected to occur over North American west
coast longitudes and Hawaii on November 17. The strong moonlight
caused difficulties in determining the limiting magnitudes, resulting
in large scatters of the ZHRs. This Circular does not claim to
give first average ZHRs -- it rather tries to find the actual peak
time. ZHRs should be treated as relative values, since more elaborate
calibration of the moonlight observations may be necessary when more
data have been received.

The peak time fell between 10h30 UT and 13h UT. The exact time is
hard to derive, since several observers reported sharp activity
peaks at different times within this period. Average rates suggest
11h UT, which is the same peak solar longitude (sol=235.17) as
in 1996. Based on the data available, it is not possible to recognize
double peaks or filamentary structures. The scatter and temporal
variations are assumed to be caused by the poor conditions we had to
face this year.

We gratefully thank all the observers who made their observations
available by sending them to the Visual Commission or publishing
them on one of the meteor mailing lists.

The ZHRs are calculated with a population index of r=2.0 and a
zenithal exponent of 1.0. A large relative scatter of rates
appears at the interface between observations from the Canary
islands and North American east coast observers, indicating a
zenithal exponent different from 1.0. Errors are the standard
deviations of the average.